Hydraulic power steering gear assembly with unloading valve

Abstract

A hydraulic power steering gear assembly includes an assembly body defining a piston chamber having opposed chamber ends with plunger passages formed in the ends, a reciprocating piston and a chamber having opposed ends and a passage extending between the piston ends, a check valve at each end of the piston passage, and a plunger assembly in each plunger passage with each assembly including a spring frictionally holding assembly in the passage and a poppet extending into the chamber to unseat a ball valve as the piston is moved toward one end of the chamber.

What I claim as my invention is: 
     
       1. A hydraulic power steering gear assembly comprising an assembly body defining a piston chamber having opposed chamber ends; a reciprocating power piston in the chamber having opposed piston ends facing said chamber ends and a rack;   an input shaft mounted in the assembly body at one chamber end and extending into the chamber from such chamber end;   a ball screw connection between the input shaft and the piston;   an output shaft rotatably mounted in the assembly body with a gear on the output shaft, said gear engaging said piston rack;   a piston passage extending through the piston between said piston ends;   a check valve at each end of the piston passage;   a plunger passage in said assembly body at each end of the chamber, such passages aligned with the ends of the piston passage; and   a plunger assembly in each plunger passage, each such assembly including a plunger body having a first end away from the chamber, a poppet end extending into the chamber, a rod extending between such ends, opposed stop members on each end of the plunger body, and a spring substantially surrounding the rod and extending between said stop members, said spring resiliently engaging a wall of a plunger passage.   
     
     
       2. A hydraulic power steering gear assembly as in claim 1 wherein each plunge passage includes a first stop surface facing away from the chamber and each plunger assembly includes a second stop surface facing the chamber, engagable with said first stop surface and located further away from the chamber than the first stop surface for preventing movement of the plunger assembly into the chamber. 
     
     
       3. A hydraulic power steering gear assembly as in claim 2 wherein one of said stop surfaces comprises a circular step. 
     
     
       4. A hydraulic power steering gear assembly as in claim 1 wherein each spring has a C-shaped cross section and includes a pair of edges. 
     
     
       5. A hydraulic power steering gear assembly as in claim 4 wherein each plunger passage includes an inwardly extending surface facing away from the chamber for preventing movement of a plunger assembly into the chamber. 
     
     
       6. A hydraulic power steering gear assembly as in claim 5 wherein each plunger assembly includes a head away from the chamber, a seal extending around the head and engaging the inner wall of a plunger passage and a reduced area drive surface facing away from the chamber. 
     
     
       7. A hydraulic power steering gear assembly as in claim 6 wherein each plunger assembly includes a stop member adjacent the poppet and a slot formed in stop member facing the poppet. 
     
     
       8. A hydraulic power steering assembly comprising a power piston in a cylinder, the cylinder having opposed ends; check valves in the piston facing the cylinder ends; a first passage in the piston communicating said check valves; an output member; an operative connection joining the piston to the output member; a pair of plunger passages in the ends of the cylinder in alignment with said check valves in said piston; and a pair of plunger bodies, each plunger body fitted in a plunger passage and including a poppet on an end of the body extending into the chamber; and a friction retention radial force spring arranged in each passage between each plunger body and the wall of the plunger passage forming a spring backed friction connection retaining such body in place in such passage while permitting adjustment movement of such body along the passage. 
     
     
       9. A hydraulic power steering assembly as in claim 8 wherein each spring is mounted on a plunger body and includes an outwardly facing surface engaging the wall of a plunger passage. 
     
     
       10. A hydraulic power steering assembly as in claim 8 wherein each plunger body includes opposed stop surfaces and each spring extends between such surfaces. 
     
     
       11. A hydraulic power steering assembly as in claim 8 wherein each spring surrounds a plunger body. 
     
     
       12. A hydraulic power steering assembly as in claim 11 wherein each spring includes an outwardly facing friction surface engaging the wall of a plunger passage. 
     
     
       13. A hydraulic power steering assembly as in claim 12 wherein each spring comprises an elongate roll pin having opposed edges extending along the length of a plunger passage, each friction surface extending substantially around a body. 
     
     
       14. A hydraulic power steering assembly as in claim 13 wherein each plunger body includes a plunger step facing the cylinder and including a step on each plunger passage facing away from the cylinder, such steps preventing movement of the plunger member into the cylinder. 
     
     
       15. A hydraulic power steering assembly as in claim 14 including a head on the end of each plunger body away from the cylinder, said each head including a seal member engaging the wall of a plunger passage, a tapered end and a drive surface smaller than the head. 
     
     
       16. A hydraulic power steering assembly as in claim 15 including a tooling-engaging feature on the drive surface. 
     
     
       17. A hydraulic power steering assembly as in claim 8 wherein each spring comprises a roll pin surrounding the plunger body, each spring engaging a plunger passage. 
     
     
       18. A hydraulic power steering assembly as in claim 17 wherein each spring is formed from rolled sheet metal and includes a pair of parallel edges closely spaced and extending along the length of the spring.